Balloon catheters are commonly used in urinary tract surgery. For example, the Foley catheter is the most common balloon type catheter, being inserted into the urethra until the catheter extends into the bladder. Then, a balloon adjacent the head is inflated to retain the catheter for usually a period of days, although catheters may need to be implanted for a longer period of time in certain situations.
Other catheters, with and without balloons, are used for gastric and other purposes.
The early designs of Foley catheters were generally made of natural rubber latex. As is known, the latex can cause a reaction in the tissues which are adjacent to it. This can be very uncomfortable for the patient, and it is, of course, undesirable from a medical viewpoint.
Some catheters have been fabricated out of silicone rubber, or out of latex which is coated with a film of silicone rubber, to avoid the tissue reaction problem. Such catheters are, however, more expensive than latex catheters, and they are also somewhat difficult to fabricate, as are latex catheters, because both of the above materials are generally not thermoplastic materials, but must be cured over a period of time to obtain the desired physical properties.
Another type of balloon catheter has a polyvinyl chloride tubular shank attached to a natural rubber latex balloon, since vinyl is unsuitable as a balloon material. Thus, the latex balloon remains as an irritant, and vinyl catheters have exhibited an undesirable "feel" to the patient.
In U.S. patent application Ser. No. 853,738, filed Nov. 21, 1977 now U.S. Pat. No. 4,154,244, a catheter which comprises an oil-filled, thermoplastic rubber material is shown which exhibits a very low toxicity so that little or no irritation is felt by the patient, and which has other advantages as well.
This present invention constitutes an improvement upon the invention of the prior art patent application in that the surface of the catheter of this invention exhibits a substantially reduced friction to the body and the like, and also exhibits a significantly reduced tendency to collect encrustation, the surface exhibiting a high degree of smoothness and gloss.
The balloon of the catheter of this invention exhibits particularly good elastomeric recovery, with low creep, so that there is little "pruning" upon deflation of the balloon, i.e. the formation of wrinkles in the balloon.
While the material of the catheter of this invention, on a cost basis, is similar to natural rubber latex and the like, it is as non-toxic as silicone rubber, thereby combining the advantages of the two types of catheters.
Also, as a further advantage, the tubular shaft of the catheter of this invention may be formed by simple extrusion, without a post cure time, since the material of the catheter may be thermoplastic, but also of a softening temperature which permits autoclaving of the catheter if desired.
Also, parts of the catheter may be thermoformed or injection molded as desired. The tubing of the catheter of this invention may be kink and collapse resistant upon aspiration and normal use, and it may be fabricated by heat sealing, without separate adhesives.
Also, the cost of fabrication of the catheters of this invention may be further reduced by the fact that scrap materials from the production of the catheter may be reused in molding or extrusion, since the material is of thermoplastic rather than of the thermoset type.
The catheters of this invention are also stable under radiation sterilization.